The automatic home refrigerator consists essentially of a double-walled box with a hinged door, the space between the walls of the box being filled with an insulating material. The outer walls, comprised of steel sheets, generally have an exterior finish of baked enamel. The interior walls, when constructed of steel sheets, are usually finished with an acid-resistant porcelain enamel.
The door is generally double-walled and insulated to offset the thermal conductivity of the materials used in its construction. A gasket on the frame maintains a seal and prevents the leakage of warm air into the box when the door is closed.
Insulated doors for refrigerators, freezers and other insulated cabinets are usually constructed of two main components; an outer "face" and an inner "drum". The hollow chamber defined by these two members is then filled with an insulation material such as a foamed polyurethane which is poured into the chamber in liquid form and foamed in-situ.
To secure the drum to the door face the most common approach has been to use screws or bolts extending through the opposed peripheral edges of the door face and the drum. Alternatively, a bridging strip may be used where the drum and face are both made of metal. In this structure the strip may be welded to the edges of the drum and the face.
Both of these approaches to assembling the door drum and face have a serious drawback in that the drum and the face, that is, the inner and outer surfaces of the insulated door, will be subjected to significantly different temperatures. For example, a freezer may be operated with its interior temperature at around 0.degree. F. or below, while the outside temperature i.e. the temperature of the room in which the freezer is located may well be 80.degree. F. or more. This results in a thermally induced relative movement between the inner and outer surfaces of the insulated door. Thus where the drum is fixed to the face by screws or other rigid fasteners, cracking and other damage to the door will often result.
Suggested solutions to this problem have included the use of a snap-in inner door liner, such as shown in U.S. Pat. No. 3,882,637, which is designed to permit relative movement between the inner and outer door components. Interfitting joints have been used between the door face and drum, as in U.S. Pat. Nos. 3,883,198 and 3,915,527. The joints are designed to permit sliding movement between the interengaging edges of the two door components.
Obviously, where the inner liner of the door is of larger size than the opening in the door face into which it is positioned (to provide a snap-in construction), special handling and manipulation of the door components during assembly is required. By the same token where an interfitting edge construction is utilized it will be apparent that these edges must be rolled or otherwise formed to provide the reversely bent edges along the door components.
A similar, related problem in the construction of insulated cabinet doors has been the attachment of the sealing gasket to the door. These gaskets are resilient and often magnetic and designed to be interposed between the inner surface of the door and the opposing portions of the cabinet to form an air-tight seal.
Quite often such gaskets are attached to the drum of the door by means of threaded fasteners, as shown in U.S. Pat. No. 3,078,003, wherein the same screws which secure the gasket to the door also secure the drum to the face of the door. A somewhat similar construction is shown in U.S. Pat. No. 3,359,053, wherein the bolts or screws which secure the drum to the door face also pass through clips which engage the gasket and hold it in place.
Both constructions present the same problems as those described above with respect to the attachment of the door drum to the door face. Namely, that by providing a rigid connection between the edges of the door drum and face, when thermally induced relative movement between these components occurs there is a tendency for the components to crack or otherwise become damaged.
Another approach is shown in French Pat. No. 1,362,178 wherein the sealing gasket also performs a second function of attachment to hold the door face and door drum together while a foamed in-situ material is cured to thereafter serve as a structural component of the door. However, with this construction, the gasket is permanently embedded in the door, rendering it virtually impossible to remove it for replacement or repair. Additionally, the protruding gasket which must be positioned in place during the foaming operation is obviously positioned such that it can be easily damaged during handling of the door immediately prior and subsequent to the foaming operation.
While the above-noted French patent also discloses an embodiment in which the gasket appears to be removable, in this embodiment the door drum and door face are not provided with securing means during the foaming operation, but are presumably held in position with respect to each other with some type of fixture which is not disclosed. Suffice it to say that maintaining the door components in the desired position solely by means of the fixture holding the door during the foaming operation would be extremely difficult if not impossible from a practical point of view.
In U.S. Pat. No. 4,053,972, the main door components i.e., the door face and drum, are interconnected without the use of threaded fasteners such as screws or bolts. Instead a hardened, insulating material which is formed in-situ forms the main interconnection between the door face and drum, thereby securing them together. In constructing the door, S-shaped retainers are used which receive in their oppositely opening loops the edges of the face and drum. Temporary spacers are then interposed between the face and drum edges for the foaming operation. Following the filling of the door cavity with insulating material the spacers are removed and an anchoring leg of a gasket is snapped into place into the cavity left by the removal of the spacers, securing the gasket to the door without the use of screws or other mechanical fasteners, but permitting the gasket to be removed as necessary for replacement or repair. This process, while accommodating thermally induced relative movement between the two main door components, entails further, more complex construction steps not required in the present invention. I have invented a door for refrigerators or the like which avoids the above-noted disadvantages.